This invention is directed to the manufacture of resonators, especially quartz crystal resonators, and is specifically directed to longitudinal resonators requiring a cylindrical bevel near each end.
The use of quartz crystals as resonators is well-known in the art. It is also well-known that various "cuts" of quartz crystals have different properties when utilized as resonators. The design of a particular resonator involves enhancing a desired mode of vibration while minimizing undesired modes. Because of the many possible modes of operation, it is often desirable to use specific geometries in order to minimize coupling undesired modes from the desired mode.
Various types of tapers, bevels, and irregular physical dimensions have been utilized to minimize undesired responses. For example, AT-cut strip quartz resonators, especially when dimensioned to operate at low frequencies, have minimized undesired modes of operation when the ends of the strip are cylindrically beveled or rounded. Normally, such strip resonators are manufactured from a uniform thickness wafer of quartz so that the beveling or rounding at the ends require the removal of material.
Such material can be removed by the use of an abrasive grinding wheel. Material can also be removed from the crystal strips by placing them in a pipe with an abrasive grit and causing the pipe to rotate about its axis. Quartz material is removed as the strips repeatedly come in contact and randomly tumble in the grit. As will be appreciated, randomly tumbling such strips in a pipe with abrasive grit may cause certain strips to have material undesirably removed in center locations while others may have insufficient materials removed at the ends.
It is an object of the present invention to provide an improved process for manufacturing resonators which require rounded ends.